Rob G. Jansen, PhD

Computer Scientist, Researcher, and Principal Investigator
U.S. Naval Research Laboratory, Washington, DC, USA

Publication Details

  1. Citation

    Rob Jansen, and Nicholas Hopper:
    Shadow: Running Tor in a Box for Accurate and Efficient Experimentation. Network and Distributed System Security Symposium, 2012.

    Author Links

    Venue Links


    Runner-up for the 2013 Caspar Bowden PET Award for Outstanding Research in Privacy Enhancing Technologies.


    Our work has transitioned to the open-source Shadow project


    Tor is a large and popular overlay network providing both anonymity to its users and a platform for anonymous communication research. New design proposals and attacks on the system are challenging to test in the live network because of deployment issues and the risk of invading users’ privacy, while alternative Tor experimentation techniques are limited in scale, are inaccurate, or create results that are difficult to reproduce or verify. We present the design and implementation of Shadow, an architecture for efficiently running accurate Tor experiments on a single machine. We validate Shadow’s accuracy with a private Tor deployment on PlanetLab and a comparison to live network performance statistics. To demonstrate Shadow’s powerful capabilities, we investigate circuit scheduling and find that the EWMA circuit scheduler reduces aggregate client performance under certain loads when deployed to the entire Tor network. Our software runs without root privileges, is open source, and is publicly available for download.


      title = {Shadow: Running Tor in a Box for Accurate and Efficient Experimentation},
      author = {Jansen, Rob and Hopper, Nicholas},
      booktitle = {Network and Distributed System Security Symposium},
      year = {2012},